Detection of biomarkers has been considered as an useful tool for diagnosis, especially for early disease diagnosis. Many sandwich immunoassays, such as electrochemiluminescence immunoassay, enzyme immunoassay, and immunoassay with fluorescence labels, such as quantum dots and commercially available fluorophores tagged antibody, have been developed for the detection of disease related to protein biomarkers.
Nonetheless, to quantify trace amount of protein biomarkers in complex sample matrix, those immunoassays often require a relatively large amount of raw sample (tens to hundreds microliter), multiple purification, pre-treatment and enrichment steps. The tedious pretreatment steps often cause sample loss and hence hindered the accuracy and throughput of the detection assay. Hence, a direct, simple, specific, sensitive and accurate detection is highly in demand. It is the objective of the present invention to provide a direct, simple, specific, sensitive and accurate detection solution.